My stable includes a 1999 XJR (Mercedes W5A580 transmission, not GM).
When started in P, it bucks - the parking pawl is set, but the transmission appears to be IN GEAR. Starting in N is alleviated, but it’s still in forward gear.
Presently, I have the back end up on jacks. I disable traction control (and must do so EACH time I start). In addition to the above observations, the transmission remains in forward even for the R selection.
Finally got the console surround out to access the Dual Linear Switch, removed that, opened it up and found nothing untoward - tracks are clean (lubed, but clean), and free of defects. Reinstalled it, then slapped together simple LED test circuit and drove pins into the plug for the switch (two pins for power, four for the bitstates being presented to the TCM), and verified that the pins are being driven to the correct states in all the gear positions. I located some pages from a 1998 “student guide” online that showed what the pin states were supposed to be for each gear.
I was really hoping for a failure in the output from the linear switch, because I could more readily backtrace and replace components on that (this linear switch is basically a handful of SMD capacitors, a fair quantity of resistors, and 10 or so transistors - it’s not like the later linear switch that appears to incorporate a microcontroller).
I had purchased a JDHT workshop CD for the XJR when I acquired it almost four years ago, but was disappointed to find that the manual was almost exclusively for engine overhauling - no trim. body, or electrics. Is there a suitable source of a manual that covers electrics?
I have an ODBII code reader (Actron CP9695), but I see only about 20 dynamic readings for this auto, no codes were being thrown (outside of a generic P1000 - no DTC definition). After doing some testing today (with the back end off the ground), I ended up getting a P0730 (gear ratio incorrect) and C1175 (LH rear wheel speed sensor fail). I question if these were thrown due to the fact that the vehicle is not mobile during the testing, I have not erased them and run more tests to see if they trigger again or not.
If I rev the engine up to a couple of thousand RPM, the speedo claims a steady speed and there’s no drop in engine RPM as I shift through the gears (avoiding Park due to the pawl, and Reverse because even if it’s spinning forward now, I’m not interested in something resolving itself). Feels rather like a valve stuck in a position, but there’s no error about that (not even a transmission failure message on the dash).
I’m seriously considering putting together something to just read the CAN bus and dump raw data, but I need to order some components for that, and would like to have better documentation first.
Other notes:
Transmission shows no signs of fluid leaks. The dipstick tube has that blasted sealed cap at the top and no dipstick, so I figure if I want a peek, I’ll have to open up somewhere else. Since the problem is forward drive in all gears rather than sluggish pickup, I’m not prone to believe the problem is low fluid level.
In searches, I see mention of dealer reflashing of the TCM. Do these normally have issues? Since the car is not drivable in its current state, it’s not like I can just cruise it on over to the nearest dealer (some 60 miles away).
Thanks!